DEV-2375: ensure web entities stop playing audio

interface/resources/qml/Web3DSurface.qml

@@ -33,6 +33,10 @@ Item {
     property var item: null
 
     function load(url, scriptUrl) {
+        // Ensure we reset any existing item to "about:blank" to ensure web audio stops: DEV-2375
+        if (root.item != null) {
+            root.item.url = "about:blank"
+        }
         QmlSurface.load("./controls/WebView.qml", root, function(newItem) {
             root.item = newItem
             root.item.url = url